Sukkot

Sukkot or Succot, in traditional Ashkenazi pronunciation Sukkos or Succos, literally Feast of Booths, is commonly translated to English as Feast of Tabernacles, sometimes also as Feast of the Ingathering. It is a biblical Jewish holiday celebrated on the 15th day of the month of Tishrei (varies from late September to late October). During the existence of the Jerusalem Temple it was one of the Three Pilgrimage Festivals on which the Israelites were commanded to perform a pilgrimage to the Temple.

chabad.org:

For forty years, as our ancestors traversed the Sinai Desert, following the Exodus from Egypt, miraculous "clouds of glory" surrounded and hovered over them, shielding them from the dangers and discomforts of the desert. Ever since, we remember G-d’s kindness and reaffirm our trust in His providence by dwelling in a sukkah - a hut of temporary construction with a roof covering of branches - for the duration of the Sukkot festival (on the Jewish calendar Tishrei 15-21). For seven days and nights, we eat all our meals in the sukkah and otherwise regard it as our home.

Another Sukkot observance is the taking of the Four Kinds: an etrog (citron), a lulav (palm frond), three hadassim (myrtle twigs) and two aravot (willow twigs). On each day of the festival (excepting Shabbat), we take the Four Kinds, recite a blessing over them, bring them together in our hands and wave them in all six directions: right, left, forward, up, down and backward. Our sages in the midrash tell us that the Four Kinds represent the various types and personalities that comprise the community of Israel, whose intrinsic unity we emphasize on Sukkot.

Sukkot is also called The Time of Our Joy; indeed, a special joy pervades the festival. nightly Water-Drawing Celebrations, reminiscent of the evening-to-dawn festivities held in the Holy Temple in preparation for the drawing of water for use in the festival service, fill the synagogues and streets with song, music and dance until the wee hours of the morning.

The seventh day of Sukkot is called Hoshaana Rabbah ("Great Salvation") and closes the period of Divine judgment begun on Rosh Hashanah. A special observance is the aravah - the taking of a bundle of willow branches.

Source: chabad.org

In 2021 Sukkot in USA falls on September 20.